Continuous Flowering Research Articles

Invertebrate and fungal associations of the pastoral weed, Madagascar ragwort, Senecio madagascariensis Poir, in Northland, New Zealand, and implications for biocontrol

ABSTRACT Senecio madagascariensis Poir is now found in New Zealand colonising pastoral habitats north of a latitude 35.5°S. This prolific, continuous flowering, toxic perennial weed may not have reached its potential geographic range in New Zealand and is poorly controlled by herbicides. Prior to embarking on a biocontrol programme for this weed, we present a survey of invertebrates and diseases which found relatively few natural enemies and no specialised herbivores or plant pathogens in its current range in New Zealand. The most significant herbivorous insect pests were Hemipteran sap-suckers from 8 families. Percentage infestation of seedheads by the multivoltine tephritid fly, Sphenella rufriceps (Macquart) ranged from 16.7% to 49.8%. Fewer stems of S. madagascariensis were found in plants infected by the fungus, Puccinia lagenophorae Cooke. A search in Western Province (RSA) and in Madagascar for biocontrol control agents host specific to S. madagascariensis is planned.

The history of the breeding of Clematis (Clematis L.) in the M. M. Gryshko National Botanical Garden, NAS of Ukraine

Purpose. Investigate the history of Clematis breeding in the M. M. Gryshko National Botanical Garden (NBG), NAS of Ukraine, determine the main directions of hybrid Clematis breeding work. Results. It was established that the result of more than 16 years of breeding Clematis in the NBG was the selection of the 61 perspective hybrid, 42 of which, the most perspective, were assigned names. Of these, large­flowered varieties are the most numerous according to the distribution of variety groups in the current Royal Horticultural Society of Great Britain classification. In particular, Late Large­flowered account for about 40% of the total and Early Large­flowered for about 29%. Small­flowered hybrids make up the smaller part, of which about 26% belong to the Viticella group and one hybrid (‘Sputnik’) to the Integrifolia. The known directions of distribution of hybrid Сlematis of the NBG breeding indicate the possibility of their successful cultivation both in continental and maritime areas with a high level of humidity in the temperate zone and in the dry Mediterranean climate of the subtropical climate zone, which reveals their significant adaptive potential. Conclusions. Obtaining varieties of hybrid Clematis of domestic breeding is important for the implementation of sustainable horticulture practices on the territory of Ukraine, since a significant part of the modern introduced assortment of Clematis raises doubts about their adaptability to the local climate, and requires additional research into their adaptive potential. A successful combination in vertical landscaping of NBG­bred Clematis belonging to different varietal groups can ensure continuous flowering from May to the end of the season. These unique characteristics of Clematis ensure the creation of not only environmentally sustainable, but also visually appealing spaces that will contribute to the overall health and beauty of the urban environment.

Impacts of novel calotropis gigantea seed biodiesel usage as a fuel substitute along with various metal-oxide nanoparticles on the DICI engine characteristics

Impacts of novel calotropis gigantea seed biodiesel usage as a fuel substitute along with various metal-oxide nanoparticles on the DICI engine characteristics

Comparative Transcriptome Analysis of Mature Leaves of Dimocarpus longan cv. ‘Sijimi’ Provides Insight into Its Continuous-Flowering Trait

Longan (Dimocarpus longan Lour.) is an important tropical and subtropical fruit, and most of its cultivars bloom once a year (once-flowering, OF). Dimocarpus longan cv. ‘Sijimi’ (SJ) is a tropical ecotype variety that blooms several times a year (continuous-flowering, CF) without the need for low-temperature induction. Several studies have focused on the mechanism of continuous flowering in SJ longan; however, none used leaves as research material. As leaves are a key organ in sensing floral-induction signals, we compared gene-expression differences between mature leaves of CF (SJ) and OF (D. longan cv. ‘Shixia’ (SX) and D. longan cv. ‘Chuliang’ (CL)) longan by transcriptome sequencing. An average of 47,982,637, 43,833,340 and 54,441,291 clean reads were obtained for SJ, SX and CL respectively, and a total of 6745 differentially expressed genes (DEGs) were detected. Following Metabolic pathways, Plant-pathogen interaction and Biosynthesis of secondary metabolites, most of the other genes were assigned to the KEGG classifications of MAPK signaling pathway- plant, Plant hormone signal transduction, Amino sugar and nucleotide sugar metabolism and Starch and sucrose metabolism. WGCNA analysis clustered genes into 27 modules, among which bisque4 and darkorange2 module genes specifically were expressed at low and high levels in SJ, respectively. Different gene-expression patterns were detected between CF and OF longan in bisque4 and darkorange2 modules, especially the high levels of transcription factor (TF) expression and the large number of gibberellic acid (GA)-signaling-pathway-specific genes expressed at high levels in CF longan (SJ). Floral-induction-gene expression levels in CF longan, such as levels of GA-signaling-related and FT genes, were always high. In CF longan, after vegetative-growth accumulation, flowers could be directly induced, thereby eliminating the need for low-temperature induction.

Fine-grained recognition of bitter gourd maturity based on Improved YOLOv5-seg model

Bitter gourd, being perishable, requires timely harvesting. Delayed harvesting can result in a substantial reduction in fruit quality. while premature harvesting leads to underdeveloped fruit and decreased yields, the continuous flowering pattern in bitter gourd underscores the significance of accurately assessing fruit growth and ensuring timely harvesting for subsequent fruit setting and development. The current reliance on the experience of production personnel represents a substantial inefficiency. We present an improved real-time instance segmentation model based on YOLOv5-seg. The utilization of dynamic snake convolution enables the extraction of morphological features from the curved and elongated structure of bitter gourd. Diverse branch blocks enhance feature space diversity without inflating model size and inference time, contributing to improved recognition of expansion stages during bitter gourd growth. Additionally, the introduction of Focal-EIOU loss accurately locates the boundary box and mask, addressing sample imbalances in the L2 stage. Experimental results showcase remarkable accuracy rates of 99.3%, 93.8%, and 98.3% for L1, L2, and L3 stages using mAP@0.5. In comparison, our model outperforms other case segmentation models, excelling in both detection accuracy and inference speed. The improved YOLOv5-seg model demonstrates strong performance in fine-grained recognition of bitter gourd during the expansion stage. It efficiently segments bitter gourd in real-time under varying lighting and occlusion conditions, providing crucial maturity information. This model offers reliable insights for agricultural workers, facilitating precise harvesting decisions.

Plant–hummingbird interaction networks in an urban area: a generalist species as the protagonist in mutualistic and agonistic interactions

ABSTRACT The maintenance of green areas within cities is essential for promoting urban biodiversity and species interactions. Here, we evaluated the interactions between hummingbirds and their visited plants over the course of a year in an urban park in Barreiras, western Bahia, Brazil. Each month, from October 2018 to September 2019, we recorded hummingbird species, the plants they visit, and their agonistic interactions. We recorded 748 legitimate visits by six hummingbirds to five plant species. Most plant species (60%) flowered continuously, and most visits were recorded in the rainy season when the network was also more specialized (H2' = 0.821). Chionomesa fimbriata was the only hummingbird recorded during all studied months. This species performed 70% of all visits recorded and was involved in most agonistic interactions (n = 68). The availability of resources affected the number of visits (p = 0.016). Tree species producing many flowers increased hummingbird diversity and concentrated most of the agonistic interactions. Plant species with continuous flowering represented a persistent supply of resources, favoring the residence of C. fimbriata within the study site. Despite the low diversity of resources, the richness of hummingbirds recorded attests to the importance of maintaining green spaces in cities to promote urban biodiversity.

Function of FT in Flowering Induction in Two Camellia Species.

FLOWERING LOCUS T (FT), belonging to the FT/TFL1 gene family, is an important gene regulating the flowering transition and inflorescence architecture during plant development. Given its importance to plant adaptation and crop improvement, FT has been extensively studied in related plant research; however, the specific role and underlying molecular mechanisms of FT in the continuous flowering of perennial plants remains elusive. Here, we isolated and characterized homologous FT genes from two Camellia species with different flowering-period phenotypes: CaFT was isolated from Camellia azalea, a precious species blooming in summer and flowering throughout the year, and CjFT was isolated from C. japonica, which blooms in winter and spring. The major difference in the genes between the two species was an additional five-amino acid repeat sequence in C. japonica. FT showed high expression levels in the leaves in both species from January to August, especially in April for C. japonica and in May for C. azalea. CaFT was expressed throughout the year in C. azalea, whereas CjFT was not expressed from September to December in C. japonica. The expression levels of FT in the floral buds were generally higher than those in the leaves. Overexpression of CaFT and CjFT in Arabidopsis indicated that both genes can activate downstream genes to promote flowering. Transgenic callus tissue was obtained by introducing the two genes into C. azalea through Agrobacterium-mediated transformation. Transcriptome and quantitative real-time polymerase chain reaction analyses indicated that both florigen FT genes promoted the expression of downstream genes such as AP1, FUL, and SEP3, and slightly up-regulated the expression of upstream genes such as CO and GI. The above results indicated that CaFT and CjFT played a role in promoting flowering in both camellia species. The expression pattern of CaFT in leaves suggested that, compared to CjFT, CaFT may be related to the annual flowering of C. azalea.

Morphological and molecular analysis of rose cultivars from the Grandiflora and Kordesii garden groups.

The breeding of remontant rose cultivars that are resistant to diseases and adverse conditions, with high decorative value and continuous flowering is the most important task during work with the gene pool of garden roses. Currently, intercultivar hybridization within a single garden group has largely outlived its usefulness. It is necessary to breed for highly decorative forms or cultivars that have outstanding resistance, morphological characters and patterns of seasonal rhythms, and use these plants as parental forms in further breeding. This study represents a comparative analysis of rose cultivars from two garden groups, Grandiflora (Gurzuf, Lezginka, Korallovy Syurpriz, Queen Elizabeth, Komsomolsky Ogonyok, Love) and Rosa Kordesii (Letniye Zvyozdy, Dortmund, Gutsulochka). These cultivars proved themselves during many years of testing in harsh climatic conditions. The objectives of the study were to determine the genetic relationship within the groups and to assign phenotypically different cultivars to one or another garden group. The analysis was carried out by morphological, phenological and ISSR markers. According to the phenological observations on the Grandiflora cultivars, Komsomolsky Ogonyok had later budding and flowering stages. Polymorphic data generated from the ISSR markers showed that this cultivar was the most distant from the others and formed a separate cluster on the dendrogram. A comparison of the morphological characters (flower diameter, number of petals, peduncle length, bush height) showed a significant difference ( p < 0.05) between Komsomolsky Ogonyok and the other Grandiflora cultivars. A dendrogram based on a molecular analysis showed a lack of close relationships between Komsomolsky Ogonyok and the Kordesii group, which formed a separate cluster. A pairwise comparison of the morphological characters in Komsomolsky Ogonyok with the Kordesii group revealed a significant ( p <0.05) difference in three of the four characters studied. The exceptions were flower diameter when comparing with Dortmund and Letniye Zvyozdy and peduncle length when comparing with Gutsulochka. Although Komsomolsky Ogonyok has a pattern of seasonal development similar to Dortmund in the Kordesii group, the molecular analysis did not assign the former to this group of roses. The cultivars that have valuable characters that no average rose does and that are phenotypically different from such roses represent the most valuable breeding material.

Genomics insights into flowering and floral pattern formation: regional duplication and seasonal pattern of gene expression in Camellia

BackgroundThe formation and domestication of ornamental traits are influenced by various aspects, such as the recognition of esthetic values and cultural traditions. Camellia japonica is widely appreciated and domesticated around the world mainly due to its rich variations in ornamental traits. Ornamental camellias have a diverse range of resources, including different bud variations from Camellia spp. as well as inter- and intra- specific hybridization. Despite research on the formation of ornamental traits, a basic understanding of their genetics and genomics is still lacking.ResultsHere, we report the chromosomal-level reference genome of C. japonica through combining multiple DNA-sequencing technologies and obtain a high-density genetic linkage map of 4255 markers by sequencing 98 interspecific F1 hybrids between C. japonica and C. chekiangoleosa. We identify two whole-genome duplication events in C. japonica: one is a shared ancient γ event, and the other is revealed to be specific to genus Camellia. Based on the micro-collinearity analysis, we find large-scale segmental duplication of chromosome 8, resulting to two copies of the AGAMOUS loci, which may play a key role in the domestication of floral shapes. To explore the regulatory mechanisms of seasonal flowering, we have analyzed year-round gene expression patterns of C. japonica and C. azalea—a sister plant of continuous flowering that has been widely used for cross breeding. Through comparative analyses of gene co-expression networks and annual gene expression patterns, we show that annual expression rhythms of some important regulators of seasonal growth and development, including GIGANTEA and CONSTANS of the photoperiod pathway, have been disrupted in C. azalea. Furthermore, we reveal that the distinctive expression patterns of FLOWERING LOCUS T can be correlated with the seasonal activities of flowering and flushing. We demonstrate that the regulatory module involved in GIGANTEA, CONSTANS, and FLOWERING LOCUS T is central to achieve seasonality.ConclusionsThrough the genomic and comparative genomics characterizations of ornamental Camellia spp., we propose that duplication of chromosomal segments as well as the establishment of gene expression patterns has played a key role in the formation of ornamental traits (e.g., flower shape, flowering time). This work provides a valuable genomic platform for understanding the molecular basis of ornamental traits.

Effect of heterologous expression of FT gene from Medicago truncatula in growth and flowering behavior of olive plants.

Olive (Olea europaea L. subsp. europaea) is one of the most important crops of the Mediterranean Basin and temperate areas worldwide. Obtaining new olive varieties adapted to climatic changing conditions and to modern agricultural practices, as well as other traits such as biotic and abiotic stress resistance and increased oil quality, is currently required; however, the long juvenile phase, as in most woody plants, is the bottleneck in olive breeding programs. Overexpression of genes encoding the 'florigen' Flowering Locus T (FT), can cause the loss of the juvenile phase in many perennials including olives. In this investigation, further characterization of three transgenic olive lines containing an FT encoding gene from Medicago truncatula, MtFTa1, under the 35S CaMV promoter, was carried out. While all three lines flowered under in vitro conditions, one of the lines stopped flowering after acclimatisation. In soil, all three lines exhibited a modified plant architecture; e.g., a continuous branching behaviour and a dwarfing growth habit. Gene expression and hormone content in shoot tips, containing the meristems from which this phenotype emerged, were examined. Higher levels of OeTFL1, a gene encoding the flowering repressor TERMINAL FLOWER 1, correlated with lack of flowering. The branching phenotype correlated with higher content of salicylic acid, indole-3-acetic acid and isopentenyl adenosine, and lower content of abscisic acid. The results obtained confirm that heterologous expression of MtFTa1 in olive induced continuous flowering independently of environmental factors, but also modified plant architecture. These phenotypical changes could be related to the altered hormonal content in transgenic plants.

A low carbon balance triggers Microvine inflorescence abscission at high temperatures

IntroductionGlobal warming is a major threat to yield sustainability in most crops, including grapevine. Whether or not grapevine fruitfulness is impaired by an imbalance between carbon supply and demand caused by high temperatures was investigated in the present study.MethodsFive experiments were conducted on Microvine, a natural mutant of grapevine that is insensitive to gibberellins, presents with a dwarf stature, and has continuous flowering along the vegetative axes. The last property was used to infer temporal patterns of inflorescence development from their spatial distribution at harvest. Two sets of plants, characterized by low or high levels of initial shoot vigor, were grown under contrasting day and night temperatures: 22°C/12°C and 30°C/20°C.Results and discussionThe rate of leaf development of the main shoot was stable, regardless of the initial vigor and temperature treatment. In contrast, the warm temperatures delayed the timing of flowering for low-vigor plants or the onset of ripening for high-vigor plants. Fruitfulness was impaired by high temperatures as a result of the abscission of young inflorescences (before the flowering stage). From a careful spatiotemporal analysis of cluster abscission, we concluded that inflorescence drop under elevated temperatures was triggered by the increase in plant carbon demand due to the oldest clusters starting to unload sugars. Elevated temperatures may have also lowered the carbohydrate supply in the zone of inflorescence abscission due to the higher leaf respiration while all organ growth demand was maintained. Interestingly, inflorescence abscission occurred earlier when whole-plant vigor was low and was followed by a recovery period, in spite of a lower non-structural sugar status than in high-vigor plants. Taken together, our results suggest that inflorescence abscission is linked to the variations of the carbon pool induced by changes in temperature and not to its absolute value. Our study, therefore, provides new hypotheses about the impacts of warm temperatures on the regulation of temperature-induced reproductive failure in grapevine.

Phenological phases of &lt;i&gt;Weigela×wagneri&lt;/i&gt; L. H. Bailey under conditions of humid subtropics in Russia

Weigela varieties of hybrid origin, known as Weigela hortensis (W. hortensis C.A. Mey) or &lt;i&gt;Weigela×wagneri&lt;/i&gt; (W.wagneri L. H. Bailey) are cultivated on the Black Sea coast of Krasnodar Krai. A current range of this beautifully flowering shrub includes more than 150 varieties. However, only 24 grow in the region and are predominately selected in the early XX century and are rarely used in the landscaping of the resort town. Ornamental varieties of Weigela grow mostly in limited use areas (Sochi Arboretum, Subtropical Botanical Garden in Kuban region, Friendship Tree Garden Museum). The study aims at investigating the phenological phases of &lt;i&gt;Weigela×wagneri&lt;/i&gt; L. H. Bailey under humid subtropical conditions of the Black Sea coast, Krasnodar Krai, to be used for the design of gardens with continuous flowering plants, as well as for breeding. The study was conducted in the period from 2013 to 2019 in the Friendship Tree Garden Museum and Subtropical Botanical Garden in Kuban region. The study involved 15 varieties of W.×wagneri. The authors established differences in phenological phases, including the start/end of growing season and flowering, duration of these periods, as well as the sums of effective temperatures required for these phases. The start of the growing season was established to vary from February 12 (Arlequin) with an accumulated sum of effective temperature of 261.2℃ to March 14 (Brictol Ruby) and a sum of temperature of 376.9℃. Differences between varieties in this phenophase account for 30 days. On the basis of the long-term average annual data, the varieties were divided into groups according to the floral initiation: early flowering (from April 14 to April 21) group included Arlequin, Gustave Malet, Mon Blanc, Newport Red, Venusta, Madame Lemoine; medium-flowering (April 22 to April 30) group included Lacepede, Ballet, Pavillon Blanc, Brictol Ruby, Madame Lemoine; Eva Ratke, Kosteriana variegata, Red Prince, Augusta were included into a late-flowering (from May 01 to May 06) group. According to the dates of the start and end of growing season, the varieties were divided into the following phenological groups: EE – Early starting (before Feb 12) and Early ending vegetation (before Dec 05); EL – Early starting (before Feb 12) and Late ending (after Dec 19); LE – Late starting (after March 4) and Early ending (before Dec 5); LL – Late starting (after March 4) and Late ending vegetation (after Dec 19).

A Real-Time Detection and Maturity Classification Method for Loofah

Fruit maturity is a crucial index for determining the optimal harvesting period of open-field loofah. Given the plant’s continuous flowering and fruiting patterns, fruits often reach maturity at different times, making precise maturity detection essential for high-quality and high-yield loofah production. Despite its importance, little research has been conducted in China on open-field young fruits and vegetables and a dearth of standards and techniques for accurate and non-destructive monitoring of loofah fruit maturity exists. This study introduces a real-time detection and maturity classification method for loofah, comprising two components: LuffaInst, a one-stage instance segmentation model, and a machine learning-based maturity classification model. LuffaInst employs a lightweight EdgeNeXt as the backbone and an enhanced pyramid attention-based feature pyramid network (PAFPN). To cater to the unique characteristics of elongated loofah fruits and the challenge of small target detection, we incorporated a novel attention module, the efficient strip attention module (ESA), which utilizes long and narrow convolutional kernels for strip pooling, a strategy more suitable for loofah fruit detection than traditional spatial pooling. Experimental results on the loofah dataset reveal that these improvements equip our LuffaInst with lower parameter weights and higher accuracy than other prevalent instance segmentation models. The mean average precision (mAP) on the loofah image dataset improved by at least 3.2% and the FPS increased by at least 10.13 f/s compared with Mask R-CNN, Mask Scoring R-CNN, YOLACT++, and SOLOv2, thereby satisfying the real-time detection requirement. Additionally, a random forest model, relying on color and texture features, was developed for three maturity classifications of loofah fruit instances (M1: fruit setting stage, M2: fruit enlargement stage, M3: fruit maturation stage). The application of a pruning strategy helped attain the random forest model with the highest accuracy (91.47% for M1, 90.13% for M2, and 92.96% for M3), culminating in an overall accuracy of 91.12%. This study offers promising results for loofah fruit maturity detection, providing technical support for the automated intelligent harvesting of loofah.

PsFT, PsTFL1, and PsFD Are Involved in Regulating the Continuous Flowering of Tree Peony (Paeonia × lemoinei ‘High Noon’)

Tree peonies are an economically important crop with flowers of high ornamental value. Most tree peony cultivars in gardens are once-flowering, and the continuous flowering (CF) trait has been revealed only in a few tree peony cultivars, such as ‘High Noon’ (‘HN’). However, the molecular mechanism underlying its CF remains unclear. Here, we demonstrated that PsTFL1 functions as a floral inhibitor via the ectopic expression of PsTFL1 in transgenic Arabidopsis thaliana plants. Our findings suggest that PsFT and PsTFL1 interact with PsFD, and the detected interactions may occur in the nucleus. Compared with the non-CF variety, the gene expression patterns of PsFT, PsTFL1, and PsFD during the flower development indicate that these three genes may be related to the CF habit in tree peony ‘HN’. These findings will aid future investigations of CF behavior and promote the breeding of tree peonies and other perennial woody plants.

RcSPL1-RcTAF15b regulates the flowering time of rose (Rosa chinensis).

Rose (Rosa chinensis), which is an economically valuable floral species worldwide, has three types, namely once-flowering (OF), occasional or re-blooming (OR), and recurrent or continuous flowering (CF). However, the mechanism underlying the effect of the age pathway on the duration of the CF or OF juvenile phase is largely unknown. In this study, we observed that the RcSPL1 transcript levels were substantially upregulated during the floral development period in CF and OF plants. Additionally, accumulation of RcSPL1 protein was controlled by rch-miR156. The ectopic expression of RcSPL1 in Arabidopsis thaliana accelerated the vegetative phase transition and flowering. Furthermore, the transient overexpression of RcSPL1 in rose plants accelerated flowering, whereas silencing of RcSPL1 had the opposite phenotype. Accordingly, the transcription levels of floral meristem identity genes (APETALA1, FRUITFULL, and LEAFY) were significantly affected by the changes in RcSPL1 expression. RcTAF15b protein, which is an autonomous pathway protein, was revealed to interact with RcSPL1. The silencing and overexpression of RcTAF15b in rose plants led to delayed and accelerated flowering, respectively. Collectively, the study findings imply that RcSPL1-RcTAF15b modulates the flowering time of rose plants.

Study on the Flower Induction Mechanism of Hydrangea macrophylla.

The flower induction of Hydrangea macrophylla "Endless Summer" is regulated by a complex gene network that involves multiple signaling pathways to ensure continuous flowering throughout the growing season, but the molecular determinants of flower induction are not yet clear. In this study, genes potentially involved in signaling pathway mediating the regulatory mechanism of flower induction were identified through the transcriptomic profiles, and a hypothetical model for this regulatory mechanism was obtained by an analysis of the available transcriptomic data, suggesting that sugar-, hormone-, and flowering-related genes participated in the flower induction process of H. macrophylla "Endless Summer". The expression profiles of the genes involved in the biosynthesis and metabolism of sugar showed that the beta-amylase gene BAM1 displayed a high expression level at the BS2 stage and implied the hydrolysis of starch. It may be a signaling molecule that promotes the transition from vegetative growth to reproductive growth in H. macrophylla "Endless Summer". Complex hormone regulatory networks involved in abscisic acid (ABA), auxin (IAA), zeatin nucleoside (ZR), and gibberellin (GA) also induced flower formation in H. macrophylla. ABA participated in flower induction by regulating flowering genes. The high content of IAA and the high expression level of the auxin influx carrier gene LAX5 at the BS2 stage suggested that the flow of auxin between sources and sinks in H. macrophylla is involved in the regulation of floral induction as a signal. In addition, flowering-related genes were mainly involved in the photoperiodic pathway, the aging pathway, and the gibberellin pathway. As a result, multiple pathways, including the photoperiodic pathway, the aging pathway, and the gibberellin pathway, which were mainly mediated by crosstalk between sugar and hormone signals, regulated the molecular network involved in flower induction in H. macrophylla "Endless Summer".

Hybrid weakness and continuous flowering caused by compound expression of FTLs in Chrysanthemum morifolium × Leucanthemum paludosum intergeneric hybridization.

Hybridization is an important evolutionary mechanism ubiquitous to plants. Previous studies have shown that hybrid polyploidization of cultivated chrysanthemum, 'Zhongshanzigui', and Leucanthemum paludosum exhibit spring-flowering traits. This study explores the function of the LpFTLs gene via the phenotype of A. thaliana after heterologous transformation of the LpFTLs gene, and analyzes the mechanism ofthe continuous flowering phenotype and heterosis of hybrid offspring. The results suggest that the flowering phenotype of hybrid offspring in spring may be related to the expression of the LpFTLs gene. Ectopic expression of Leucanthemum paludosumLpFTLs in Arabidopsis thaliana resulted in earlier flowering, indicating that the LpFTLs gene also affects the flowering time in L. paludosum. Compound expression of FTLs in C. morifolium × L. paludosum intergeneric hybridization directly leads to serious heterosis in the hybrid offspring. Moreover, continuous flowering appears to be accompanied by hybrid weakness under the balance of vegetative and reproductive growth. Therefore, in future studies on chrysanthemum breeding, a suitable balance point must be established to ensure the target flowering time under normal growth.

Genome-Wide Identification and Characterization of the GRF Gene Family in Melastoma dodecandrum.

Growth-regulating factor (GRF) is a kind of transcription factor unique to plants, playing an important role in the flowering regulation, growth, and development of plants. Melastoma dodecandrum is an important member of Melastomataceae, with ornamental, medicinal, and edible benefits. The identification of the GRF gene family in M. dodecandrum can help to improve their character of flavor and continuous flowering. The members of the GRF gene family were identified from the M. dodecandrum genome, and their bioinformatics, selective pressure, and expression patterns were analyzed. The results showed that there were 20 GRF genes in M. dodecandrum. Phylogenetic analysis showed that the 71 GRF genes from M. dodecandrum, Arabidopsis thaliana, Camellia sinensis, and Oryza sativa can be divided into three clades and six subclades. The 20 GRF genes of M. dodecandrum were distributed in twelve chromosomes and one contig. Furthermore, the gene structure and motif analysis showed that the intron and motif within each clade were very similar, but there were great differences among different clades. The promoter contained cis-acting elements related to hormone induction, stress, and growth and development. Different transcriptomic expression of MdGRFs indicated that MdGRFs may be involved in regulating the growth and development of M. dodecandrum. The results laid a foundation for further study on the function and molecular mechanism of the M. dodecandrum GRF gene family.

Breeding and Selection of Nursery Plants Assisted by High-Throughput Field Phenotyping Using UAV Imagery: Case Studies with Sweet Box (Sarcococca) and Garden Rose (Rosa)

Breeding and selection of nursery plants require evaluation of a wide variety of traits. Characteristics that are visually scored in the field include aesthetic beauty as well as tolerance to (a)biotic stresses, among others. This work proposes methodologies based on vegetation indices and canopy height data derived from visual imagery captured using an RGB (red, green, blue) camera embedded in a drone to rank and select genotypes. This approach relies on quantitative evaluation standards that exclude breeder bias and speed up data collection. A proof of concept for nursery plants was developed in two woody ornamentals: sweet box (Sarcococca Lindl.) and garden rose (Rosa L.). This work aimed to compare methodologies and to propose how drones (unmanned aerial vehicles, UAV) and high throughput field phenotyping (HTFP) can be used in a commercial plant selection program. Data was gathered in 2019 in three well-established breeding trials, two for sweet box and one for rose. Characteristics discussed include plant architecture traits such as plant height and shape in the sweet box and rose as well as floribundity, continuous flowering and disease resistance in roses. Correlations were calculated between on-ground measurements and UAV-derived methods, obtaining significant results. The advantages and disadvantages of the methodology and the approach for each of the traits are discussed.

High-Throughput Sequencing Reveals Novel microRNAs Involved in the Continuous Flowering Trait of Longan (Dimocarpus longan Lour.).

A major determinant of fruit production in longan (Dimocarpus longan Lour.) is the difficulty of blossoming. In this study, high-throughput microRNA sequencing (miRNA-Seq) was carried out to compare differentially expressed miRNAs (DEmiRNAs) and their target genes between a continuous flowering cultivar 'Sijimi' (SJ), and a unique cultivar 'Lidongben' (LD), which blossoms only once in the season. Over the course of our study, 1662 known miRNAs and 235 novel miRNAs were identified and 13,334 genes were predicted to be the target of 1868 miRNAs. One conserved miRNA and 29 new novel miRNAs were identified as differently expressed; among them, 16 were upregulated and 14 were downregulated. Through the KEGG pathway and cluster analysis of DEmiRNA target genes, three critical regulatory pathways, plant-pathogen interaction, plant hormone signal transduction, and photosynthesis-antenna protein, were discovered to be strongly associated with the continuous flowering trait of the SJ. The integrated correlation analysis of DEmiRNAs and their target mRNAs revealed fourteen important flowering-related genes, including COP1-like, Casein kinase II, and TCP20. These fourteen flowering-related genes were targeted by five miRNAs, which were novel-miR137, novel-miR76, novel-miR101, novel-miR37, and csi-miR3954, suggesting these miRNAs might play vital regulatory roles in flower regulation in longan. Furthermore, novel-miR137 was cloned based on small RNA sequencing data analysis. The pSAK277-miR137 transgenic Arabidopsis plants showed delayed flowering phenotypes. This study provides new insight into molecular regulation mechanisms of longan flowering.